Rashi on the Prophets and Writings

And he commanded Judah to seek unlike the Ten Tribes, who sought other, new Gods, which came up of late, and did not seek the God of their fathers.

as long as the land is before us As long as the kingdom is established before us, so that if we need them, they will be a refuge for us. And all this happened in the ten years about which it is written (above 13:23): “in his time the land was tranquil.” But after those ten years, there was a war between him and Baasha all their lives, for in the third year of Asa, Baasha reigned, and seven years there was peace between them, and so it is proven here as well (verse 5): “and there was no war with him in these years.” But in the other years there was war with him, and below (15:19) it is written: “And there was no war until the thirty-fifth year of Asa’s reign.” We can, however, explain that the war that he had with the Cushites was not until the thirty-fifth year of his reign, but this is difficult to me, for it is written below (16:1): “In the thirty-sixth year of Asa’s reign, Baasha...advanced,” until (verse 9): “you have dealt foolishly concerning this, for from now on there will be wars with you.” It appears from here that prior to this, he did not have wars, and he lived after that only five years, and in I Kings 15:32, it is written: “And there was war between Asa and Baasha, etc. all their lives.” In Seder Olam (ch. 16) it is explained clearly.
for we sought the Lord our God; we sought [Him] Since we sought Him, He gave us peace from round about.
So they built cities.
and prospered And a similar instance is (above 12:7): “And when the Lord saw that they had humbled themselves, etc.”

it makes no difference to You to aid i.e., even though we are few and they are as numerous as the sand by the sea, and we have no strength before them, You can help both the great and the powerless; it is known that You have strength to aid; therefore, help us, O Lord our God, for we have relied on You.
let no man rule against You Let not our enemies - man - have human strength to rule (עִמְּךָ) with You, i.e., against You, to be victorious, so that they should not say, “We have defeated their God.” Another explanation from the Rabbi: Let not the weak one (אֱנוֹשׁ) be held back (יַעְצר), for we are weak, deprived of strength, keeping us back (עוֹצְרֵי יָד) from defeating them. And an example is (Deut. 11:17): “and He will hold back (וְעָצַר) the heaven”; (Gen. 20:18): “For the Lord had held back (וְעָצר עָצַר),” and like (Jud. 13:16): “If you take me in (תַּעְצְרֵנִי).”